In this paper we derive the probability of correct packet reception and the resulting channel throughput achievable in an asynchronous slow-frequency-hopped multiple user channel. Reed- Solomon coding is used to correct errors caused by other user interference in an otherwise noiseless channel. We analyze and evaluate an M-ary FSK signaling scheme, which permits the discrimination against interfering signals that are present for a sufficiently small fraction of the hop duration, and results in substantial increases in channel throughput over previous models.